1. Field of the Invention
The present invention relates to an electric rotary shaver and more particularly to a structure for supporting outer cutters in a cutter frame of the electric rotary shaver.
2. Prior Art
FIG. 7 is a perspective view of the overall structure of a prior art electric rotary shaver. In this electric shaver 10, a cutter head 20 is detachably mounted on the upper portion of a main body case 12 of the shaver 10. Three outer cutters 22 are disposed in the cutter head 20 so that the centers of the outer cutters are at the positions of the vertices of an equilateral triangle. A plurality of slits for introducing whiskers are formed in the radial direction in the outer cutters 22. Furthermore, in each outer cutter 22, an annular outside hair introduction region V and an annular inside hair introduction region W are formed in a concentric configuration, and a groove is formed in the boundary area between the outside hair introduction region V and the inside hair introduction region W.
FIG. 8 shows the internal structure of the electric rotary shaver 10. The cutter head 20 is constructed from a cutter frame 30, metal outer cutters 22, outer cutter holders 24 which hold the outer cutters 22, metal inner cutters 26, inner cutter bases 28 that support the inner cutters 26, and cutter retaining plates 31 that hold the inner cutters 26 so that the inner cutters 26 are rotatable. The cutter frame 30, outer cutter holders 24, inner cutter bases 28 and cutter retaining plates 31 are all made of a synthetic resin. The outer cutters 22 are supported so that they are prevented from rotating relative to the outer cutter holders 24, thus ensuring that the outer cutters 22 do not rotate together with the inner cutters 26.
The reference numeral 32 is a cutter cradle that is installed to cover the opening of the main body case 12. Inner cutter drive shafts 34 that transmit the rotational driving force of a motor 50 to the inner cutters 26 protrude from the cutter cradle 32 so that the respective drive shafts 34 positionally correspond to the respective inner cutters 26. The inner cutter drive shafts 34 are provided so as to be coaxial with the inner cutter bases 28 and engage with the inner cutter bases 28 in a dovetail engagement so that each of the inner cutter drive shafts 34 rotates as a unit with the corresponding inner cutter base 28.
The reference numeral 36 is a spring that constantly urges the corresponding inner cutter drive shaft 34 upward. The outer cutters 22 are supported in a floating fashion by the springs 36 via the inner cutters 26, inner cutter bases 28 and inner cutter drive shafts 34.
The linkage of the inner cutter drive shafts 34 and motor 50 is accomplished by a structure in which engaging projections 38 disposed on the outer circumferences of the lower ends of the inner cutter drive shafts 34 engage with a plurality of shaft engaging portions 42 disposed in upright positions on the inner cutter drive gears 40, and the inner cutter drive gears 40 engage with a gear 52 fastened to the output shaft of the motor 50. The inner cutter drive shafts 34 are disposed so as to tilt in all directions with respect to the axial lines of the inner cutter drive gears 40.
As described above, the outer cutters 22 are supported while being biased by the springs 36 in a direction that causes the outer cutters 22 to protrude toward the outside, so that the outer cutters 22 is movable in and out of the outer cutter holders 24 and the outer cutters 22 can tilt within a specified angular range in all directions inside the outer cutter holders 24. Furthermore, as seen from FIG. 8, the outer cutters 22 are provided, together with the outer cutter holders 24, inside the outer cutter holes 44 formed in the cutter frame 30. The internal diameter of the outer cutter holes 44 is slightly larger than the external diameter of the outer cutters 22. Accordingly, the outer cutters 22 can move inward and outward along the axial lines of the outer cutter holes 44. Also, the outer cutters 22 can tilt within a specified angular range in all directions with respect to the axial direction of the outer cutter holes 44.
The outer cutters 22 are, as described above, supported, together with the outer cutter holders 24, in the cutter frame 30 so that the outer cutters 22 can tilt and also move inward and outward in the axial direction. Accordingly, during the use, the outer cutters 22 fit against the skin as a result of the appropriate inward and outward movement and tilting movement of the outer cutters 22 in arbitrary directions when the electric shaver is placed against the jaw or cheek, so that whiskers can be reliably shaved.
In the conventional electric shaver, as seen from the above, the fact that the outer cutters 22 can tilt relative to the cutter frame 30 results from the structure in which the internal diameter of the outer cutter holes 44 is slightly larger than the external diameter of the outer cutters 22, so that the resulting clearance allows the tilting.
However, there is a demand for a product that has an even greater tilting angle of the outer cutters 22 than a conventional product, so that shaving can be accomplished with the outer cutters 22 fitted more closely to the skin. One conceivable method of meeting this demand is to increase the clearance between the outer cutter holes 44 and the outer cutters 22 to a greater value than that used in the conventional electric shavers, thus increasing the tilting angles. However, an increase of the clearance between the outer cutter holes 44 and outer cutters 22 to a larger value makes it difficult to set the center positions of the outer cutters 22 because of looseness between the outer cutter holes 44 and outer cutters 22. Also, it destabilizes the rotation of the inner cutters 26. Furthermore, the outer cutters 22 tend to make a considerable movement inside the outer cutter holes 44, lowering the cutting efficiencies.
The present invention eliminates the above problems. The object of the present invention is to provide an electric rotary shaver with a good cutting efficiency in which the outer cutters are supported so as to move axially and tilt with respect to the cutter frame, and in which the outer cutters have an increased tilting angles compared to that in a conventional shaver, thus improving the fit of the outer cutters against the skin.
In order to accomplish the above-described object, the shaver of the present invention has the structure as described below.
More specifically, the shaver of the present invention comprises:
a cutter frame provided with outer cutter holes, and
outer cutters each of which being fitted in each of the outer cutter holes so as to be movable in an axial direction thereof and tiltable in any desired direction with inner cutters provided between the outer cutters and inner cutter drive shafts, the drive shafts being urged toward outside in an axial direction thereof; and in the present invention,
the outer surfaces of the outer cutters and the inner surfaces of the outer cutter holes are formed so as to make a sliding contact, thus supporting the outer cutters in the outer cutter holes so that the outer cutters can tilt in any desired direction.
In the present invention, the outer surfaces of the outer cutters and the inner surfaces of the outer cutter holes make a sliding contact at three or more points, thus supporting the outer cutters in the cutter frame with the outer cutters being tiltable in any desired direction.
Furthermore, in the present invention, the outer cutters make a sliding contact with the inner surfaces of the outer cutter holes so that the outer cutters are movable in the axial direction.
In addition, in the present invention, resin molded sections whose outer surfaces make the sliding contact with the inner surfaces of the outer cutter holes are integrally resin-molded on the outer cutters of the outer cutters.
In the present invention, further, the outer surfaces of the outer cutters are formed in a spherical surface shape that protrudes outward, ribs that make a sliding contact with the inner surfaces of the outer cutter holes are disposed on the outer surfaces of the outer cutters so that the ribs protrude form the outer surfaces, and the outer surfaces of the outer cutters have recessed surfaces that make a sliding contact with protruding portions formed on the inner surfaces of the outer cutter holes.